How to cast[proc() {.closure, gcsafe, locks: 0.}](pointer)()?

[javinyang]

` import system proc testCallback(arg: int): proc() {.closure, gcsafe, locks: 
0.} = result = proc() {.closure, gcsafe, locks: 0.} = echo "res", arg var p1 = 
testCallback(5) var p1Pointer = system.rawProc(p1) # How to cast back 
cast[proc() {.closure, gcsafe, locks: 0.}](p1Pointer)() `

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